Cardiovascular disease is the largest cause of death world-wide. Coagulation, the process by which blood forms clots, involves a cascade of interactions between blood platelets and various coagulation factors. Physiologically, blood coagulation serves to control blood loss from a damaged vessel. In many patients, however, inhibition of blood coagulation using blood-thinning medication (anticoagulants) such as warfarin is required to reduce the risk for stroke, pulmonary embolism, heart attack, and other life-threatening cardiovascular diseases. Constant monitoring of long-term anticoagulation efficacy is critical for these patients. If the anticoagulant drug level is too low, the risk of blood clot formation is high, if the drug level is too high, severe bleeding (hemorrhage) can occur. Traditionally, oral anticoagulation therapy (OAT) is monitored by quantifying the prothrombin time expressed in international normalized ratios (INRs). These measurements are usually performed by trained specialists in a hospital or laboratory setting that meets the federal regulatory requirements.
Point of care (POC) testing devices that can be used in a caregiver's office or at home by properly selected and trained patients or their caregivers can reduce costs and improve patient outcomes. For example, this approach may provide increased convenience for the patient, rapid test results, frequent monitoring of anticoagulation efficacy to reduce the risk of bleeding or thrombotic complications (even if the patient is traveling for extended periods or is located in areas with a low density of healthcare facilities), and overall reduced cost of care.
Existing portable coagulation monitoring devices require access to a power source in order to allow reading of test results and are quite expensive, in the $1-2 k range, making them beyond the reach of a large segment of the population. Low-cost blood coagulation diagnostic testing devices and methods are needed.